Metallic getter compositions



;oxygen and carbon.

Patented Aug. 19, 1952 QEIETER .coi osnmnsg I liloyd n;- Lockwood; I Townslii Essex- County, N. J., assignorto Tungfs ol 'liamp- Works, Inc., Newark, N.' 1., a corporationi ofii :ENQ Applicationll'ecemb'er 30, 1949;

.. I :Seriak leans finee biect oi. the inven iens siasn kandmllrev esettmgneint inr h mhiest of the intentio 51a: nave and improved binder for metallicgetter powders.

A further object" of the invention is a novel and improved binder fonmetallic getter powders wliichsalswactaamagetter;

A further objector)! .the. invention is a novel method of making a paint'ofthe above indicated qh V v these binding materials eventually release carbon which if taken out of the lamp or envelope in the gas form does no damage but if carbon is left behind in the lamp envelope it tends to form or forms tungsten carbide. Tungsten carbide is very brittle and having a different coefficient of expansion from that of tungsten, of which the filament is made. causes the tungsten to distort or become distorted. This in turn results in broken filaments and unduly short life.

Regardless of how good or efiective the metallic getter powder is, the results in lamps have not been satisfactory and I have found that this is due to the effect of the presence of carbon released from the binders. I have found that a satisfactory lamp getter must take care of or get out of the lamp three things instead of ,the two we usually consider. They are hydrogen.

.A number of metallic powders make good letters and of these zirconium is probably the best and most satisfactory. It is capable of taking up hydrogen, oxygen and carbon at the temperatures found on miniature lamp lead wires as, for example, lead wires of nickel. The problem which has not hitherto been satisfactorily solved is to put this powder on nickel lead wires and keep it there so distributed that it can efiectively act on all three elements, namely hydrogen, oxygen and carbon without adding any more harmful materials.

'G'tlier binders and suspending mediums lmada dition to those mentioned above-- -have; beerr proposed as; for example, silicates, likevsodiumsilicate, but all suchbinders with which 1 18111 familiaraddwater to the getteriwhichtmam-be eitheradd 'water on phosphoric acid wliicli 1s also undesirable in lamp making. Moreover, noneaof :the' priori'bindersgmullosedi or used with which I am familiar acts alsmaa;

a getter in addition to the binding functiom.

II-have; found 'thatzspotassium. 'fiuozirconate (KziZI'Fe) P has-aideall characteristics for-:.a: ;binden and in: additionacts: as a; getter:.; FIthmmaterial is a fine white powder which does not absorb water. When mixed with alcohols, acetates, lactates and other solvents this material forms an emulsion which helps to hold the metal powders in suspension. The mixture makes a nice painting or spraying medium applied as a thin continuous film. As the liquids evaporate this material forms crystals that hold the metal powders to the nickel leads. As the lamps are processed and heat is applied during the sealing and exhaust operations no further action apparently takes place. When the filaments are burned the extra heat changes the salt from White to dark grey. After this change the getter is porous but is fastened to the nickel wire very tightly requiring decided force to break it loose. The extra heat probably breaks the double fluoride apart, the potassium fluoride forming large porous crystals which hold the metal powder in place but will not break down until a temperature of 1200 C. or above is reached. The zirconium fluoride is probably a gas at 500 C., the temperature which the lamp leads ordinarily reach while burning. This either recrystalizes at a lower temperature or breaks up, releasing metallic zirconium and fluorine gas which are both active getters. While this is probably the correct theory of the functioning of the binder and the paint it is understood that the functioning may vary from the theory above expressed.

Any suitable method of forming the getter paint may be employed. The following is a suitable method of making a getter paint embodying potassium fiuozirconate as the binder which may be applied by painting the same on the structure with a brush. To 300 grams of potassium fiuozirconate, 180 cc. of propanol and cc. of ethyl lactate are added. This mixture is then thoroughly mixed and treated by treating and mixing the same in a small ball mill for a suitable period. This period may be for sixteen hours or less. To this mix is added around 1200 grams zirconium powder, dampened with propanol and ethyl lactate as, for example, around 480 cc. propanol and 320 cc. ethyl lactate. The whole is thoroughly mixed in any suitable manner; Thepaint is then ready for application by brush. it may be conveniently storedfor use in bottles as, for example, bottles of 100 cc.

capacity. J

'dered metal zirconium exceeding the weight of the potassium fluozirconate in the paint.

If instead of applying the paint by brush it is desired to spray it on the lamp structures or parts involved, a difierent set of thinners isdesirable; or necessary to increase the drying speed. For

example, a, good spray mixture could be made by taking 100 cc. of the brush on mix and adding 100 cc. of butyl acetate, 150 cc. of ethyl alcohol, and 50 cc. of ether.

Another mixture that would be good could acetate, and 4 parts methanol. The solids should be thinned down to about the same specific gravity as-the above-mixture. p Y rSpecial precautions must be observed inthe use or handling of metallic zirconium as, for example, all water must be removed, without drying thepowder. This maybe doneby decanting with either methanol or propanol, In: addition, if 10% aluminum silicate or other inert material is added to the zirconium the wholekbatch may be milled together safely, thus making .a smoother mix;

I claim: 1. A getter paint comprising about l200parts by weight of metallic zirconium lpowder dampened with propanol and ethyl lactate; and thorbe made up using 1 part ethyl lactate, 3 parts amyl 4 oughly admixed with 300 parts by weight of potassium fiuorzirconate, in about 180 parts by volume of propanol and parts by volume of ethyl lactate.

2. A getter paint comprising powdered metallic zirconiumlthoroughly admixed with potasivhicle to form a non-viscous liquid for coating smooth metal surfaces, the weight of the pow- V LLOYD D. LOCKWOOD.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS 'OTH ER' REFERENCES i 1 Mellor, Comprehensive Treatise on Inorganic and Theoretical Chem., 1927, vol. and 140. H

7. pa es-. 

2. A GETTER PAINT COMPRISING POWDERED METALLIC ZIRCONIUM THOROUGHLY ADMIXED WITH POTASSIUM FLUOZIRCONATE AS A BINDER AND DISPERSED IN A SUFFICIENT AMOUNT OF A VOLATILE ORGANIC SOLVENT VEHICLE TO FORM A NON-VISCOUS LIQUID FOR COATING SMOOTH METAL SURFACES, THE WEIGHT OF THE POWDERED METAL ZIRCONIUM EXCEEDING THE WEIGHT OF THE POTASSIUM FLUOZIRCONATE IN THE PAINT. 